Route to hybrid cotton production

ABSTRACT

An improved procedure utilizing a cytoplasmic-genetic male sterile system for forming F 1  hybrid cottonseeds (i.e., seeds capable of forming hybrid cotton plants of the first filial generation) is provided which is readily amenable to the determination and maintenance of the desired level of purity in the hybrid cottonseed product. The parent plants required for hybrid formation are each homozygotes (as described) with respect to differing leaf shape configurations (i.e., the male sterile female parent plants have a broad-leafed configuration and the fertility-restoring male parent has a narrow-leafed configuration). The resulting F 1  hybrid cotton plants are heterozygotes with respect to leaf shape phenotype and can be visually differentiated from each parent. Following the F 1  hybrid-forming cross-pollination, at least a portion of the resulting cottonseeds are grown, and the approximate proportion of F 1  hybrid cottonseeds present in the cottonseed product is determined on the basis of the respective leaf shapes which are exhibited. The plurality of the hybrid-forming parental lines additionally can be enhanced with ease through an observation of the respective leaf shape configuration followed by the timely removal of contaminant cotton plants which lack the requisite leaf configuration. The process of the present invention accordingly provides an efficient route to overcome quality control difficulties heretofore associated with hybrid cotton production in the prior art.

BACKGROUND OF THE INVENTION

It is well known that when different plant lines are cross-pollinated,one can achieve in the offspring a highly desirable heterosis or hybridvigor which advantageously provides increased yields of the desiredcrop.

Representative crops which have been successfully hybridized in the pastinclude sugar beets, corn (See, U.S. Pat. No. 3,753,663 to Jones),sorghum, alfalfa (See, U.S. Pat. No. 3,570,181 to Davis), wheat,sunflowers, cotton, rice (See, U.S. Pat. No. 4,305,225 to Yuan),cucumbers, onions, carrots, and tomatoes.

It is well-recognized that cotton (plants of genus Gossypium) is animportant crop which is grown in many parts of the world. While thenecessary plants for hybrid cottonseed production are known andavailable, only limited hybrid cotton production has been carried out todate. For instance, in some parts of the world cotton plants have beenemasculated by hand and the pollen has been transferred to the femaleparent by hand.

While the necessary cotton plants for a cytoplasmic-genetic male sterilesystem for hybrid cottonseed production are known and available, suchsystem has heretofore been largely impossible to reliably implement on acommercial basis since it has proven to be a tremendous undertaking tomonitor the level of hybridization in the final cottonseed product andto determine and maintain purity in the parental lines.

Heretofore, most commercially grown cotton varieties have been thebroad-leafed varieties. However, it has been recognized that under somegrowing conditions the narrow-leafed cotton varieties (e.g., Pronto andGumbo) may perform better. For instance, when the growing conditions arehighly conducive to cotton boll rot, then the more open canopy growthhabit of the cotton plants made possible with the narrow-leafed cottonvarieties may be preferable. Such openness will better enable sunlightto reach the cotton bolls and for the plant to better receive aninsecticide at its innermost locations. Also, studies have beenconducted in the past with respect to insect visitation preferencesconcerning broad- and narrow-leafed cotton varieties. For a recentdiscussion of the effects of cotton leaf shape on yield see "Influenceof Leaf Morphology on Lint Yield of Cotton-Enhancement by the Sub OkraTrait," William R. Meredith Jr., Crop Science, Vol. 24, p. 855 to 857,Sept.-Oct. 1984.

Representative prior publications which concern the formation of hybridcottonseeds are the following:

(1) Canadian Pat. No. 668,452, "Production of Hybrid Cottonseed," FrankM. Eaton, Aug. 13, 1963.

(2) Vesta G. Meyer, "Male Sterility From Gossypium harknessii," J. ofHeredity, Vol. 66, p. 23 to 27 (1975).

(3) Joseph O. Moffett, Lee S. Stith, and Charles W. Shipman, "ProducingHybrid Cotton Seed on the High Plains of Texas," Beltwide CottonProduction Research Conferences Proceedings, Atlanta, Ga., p. 90 to 92(1977).

(4) J. B. Weaver, Jr., "Present Status of Fertility Restoration inCytoplasmic Male-Sterile Upland Cotton," Beltwide Cotton ProductionResearch Conferences Proceedings, Atlanta, Ga., p. 95 to 96 (1977).

(5) Joseph O. Moffett, Lee S. Stith, and Charles W. Shipman, "ProducingHybrid Cotton Seed on a Field Scale by Using Honey Bees as Pollinators,"Beltwide Cotton Production Research Conferences Proceedings, Dallas,Tex., p. 77 to 79 (1978).

(6) W. R. Meredith, Jr., Vesta Meyer, B. W. Hanny, and J. C. Bailey,"Influence of Five Gossypium Species Cytoplasms on Yield, YieldComponents, Fiber Properties, and Insect Resistance in Upland Cotton,"Crop Science, Vol. 19, p. 647 to 650, Sept.-Oct. 1979.

(7) Richard H. Sheetz and James B. Weaver, Jr., "Pima Fertility EnhancerFactor: Inheritance and Use in Hybrid Cotton Production," BeltwideCotton Production Research Conferences Proceedings, St. Louis, Mo., p.82 (1980).

(8) R. H. Sheetz and J. B. Weaver, Jr., "Inheritance of a FertilityEnhancer Factor From Pima Cotton When Transferred Into Upland CottonWith Gossypium harknessii Brandegee Cytoplasm," Crop Science, Vol. 20,p. 272 to 275, Mar.-April 1980.

(9) Delbert C. Hess, "Hybrid Cotton Development," Beltwide CottonMechanization-Production Research Conferences Proceedings, New Orleans,La., p. 28 to 29 (1981).

(10) J. E. Quisenberry and R. E. Dilbeck, "Stormproof Boll in UplandCotton III. Genotype-Environment Interaction and Genetic Analysis," CropScience, Vol. 21, p. 511 to 514, July-August 1981.

(11) James B. Weaver, Jr., "Recent Significant Observations on theDevelopment of Hybrid Cotton," Beltwide Cotton Production ResearchConferences Proceedings, Las Vegas, Nev., p. 88 to 90 (1982).

(12) James B. Weaver, Jr., "Interspecific Hybrid Cotton as a Trap Cropfor Boll Weevil Control," Beltwide Cotton Production ResearchConferences Proceedings, Las Vegas, Nev., p. 207 to 209 (1982).

(13) Frank L. Carter, Dick D. Davis and Elbert R. Jaycox, "Effect ofPlanting Pattern on Cross Pollination in Hybrid NX-1 Seed Production,"Beltwide Cotton Production Conferences Proceedings, Atlanta Ga., p. 130to 131 (1984).

(14) J. B. Weaver, "Hybrid Cotton Sets a Good Weevil Trap," ProgressiveFarmer, August 1984.

Representative prior publications which concern to at least some degreeleaf shape configurations in cotton plants are the following:

(1) J. A. Andries, J. E. Jones, L. W. Sloane, and J. G. Marshall,"Effects of Okra Leaf Shape on Boll Rot, Yield and Other ImportantCharacters of Upland Cotton, Gossypium hirsutum L., " Crop Science, Vol.9, p. 705 to 710, Nov.-Dec. 1969.

(2) J. A. Andries, J. E. Jones, L. W. Sloane, and J. G. Marshall,"Effects of Supra Okra Leaf Shape on Boll Rot, Yield, and OtherCharacters of Upland Cotton, Gossypium hirsutum L.," Crop Science, Vol.10, p. 403 to 407, July-Aug. 1970.

(3) J. E. Jones, "Effect of Morphological Characters of Cotton onInsects and Pathogens," Beltwide Cotton Production Research ConferencesProceedings, Las Vegas, Nev., p. 88 to 92 (1972).

(4) J. E. Jones, W. D. Caldwell, M. R. Milam, and D. F. Clower, "Gumboand Pronto: Two New Open-Canopy Varieties of Cotton," Circular No. 103,Louisiana State University, December 1976.

(5) W. D. Caldwell, D. R. Melville, A. M. Pavloff, and J. E. Jones,"Agronomic Studies of Okra and Super Okra Leaf Cotton," Beltwide CottonProduction Research Conferences Proceedings, Las Vegas, Nev., p. 83 to84 (1977).

(6) L. S. Bird, F. M. Bourland, R. G. Percy, J. E. Hood, and D. L. Bush,"Additional Progress in Developing Okra Leaf, Frego Bract and GlabrousMulti-Adversity Resistant Cottons," Beltwide Cotton Production ResearchConferences Proceedings, Atlanta, Ga., p. 107 to 109 (1977).

(7) J. B. Weaver, Jr., "Observations on Bee Activity in SeveralGenotypes of Cotton," Beltwide Cotton Production Research ConferencesProceedings, Dallas, Tex., p. 76 to 77 (1978).

(8) Jack E. Jones, D. T. Bowman, J. W. Brand, W. D. Caldwell, and D. F.Clower, "Genetic Improvement of Open-Canopy Cottons," Beltwide CottonProduction Research Conferences Proceedings, St. Louis, Mo., p. 72 to 74(1980).

(9) F. Karami, D. R. Krieg, and J. E. Quisenberry, "Water Relations andCarbon-14 Assimilation of Cotton With Different Leaf Morphology," CropScience, Vol. 20, p. 421 to 426, July-Aug. 1980.

(10) Jack E. Jones, "The Present State of the Art and Science of CottonBreeding for Leaf-Morphological Types," Beltwide Cotton ProductionResearch Conferences Proceedings, Las Vegas, Nev., p. 93 to 99 (1982).

The following articles mention the use of narrow leafshaped cottonplants during the production of hybrid cotton:

(1) J. B. Weaver, Jr., and Ralph Graham, "Behavior of Boll Weevils onCytoplasmic Male-Sterile Cotton in Isolated Plots," Beltwide CottonProduction Research Conferences Proceedings, Atlanta, Ga., p. 100 to 102(1977).

(2) K. N. Gururajan and K. Srinivasan, "Note on the Use of Okra-LeafMale-Sterile Line in the Production of Hybrid Cotton," Indian J. Agric.Sci., Vol. 52(1), p. 20 to 21, January 1982.

In Article (1) the use of cytoplasmic male sterile cotton plants havinga narrow leaf configuration as a trap crop for insects is mentioned. InArticle (2) the possible worth of the okra leaf character with respectto cotton yield is discussed. Each of the articles is silent withrespect to an overall commercially practicable process wherein thepurity of the hybrid cottonseed product is determined and/or controlledduring its production by any means.

It is an object of the present invention to provide an improved processfor forming F₁ hybrid cottonseeds which is capable of being readilyimplemented on a commercial scale.

It is an object of the present invention to provide an improved processfor forming F₁ hybrid cottonseeds on an efficient basis wherein thedegree of purity of the product readily can be determined on a reliablebasis.

It is an object of the present invention to provide an improved processfor forming F₁ hybrid cottonseeds on an efficient basis wherein theparent plants optionally can be grown in bulk in the same area and thedegree of hybrid purity in the product readily can be determined on areliable basis.

It is an object of the present invention to provide an improved processfor forming F₁ hybrid cottonseeds on an efficient basis wherein sourcesof non-hybrid contamination in the product readily can be identified asto their likely source.

It is an object of the present invention to provide an improved processfor forming F₁ hybrid cottonseeds on an efficient basis wherein in apreferred embodiment contamination in the parental lines readily isidentified and is eliminated so as to enhance their purity and thepurity of the F₁ hybrid cottonseed product.

It is an object of the present invention to provide an improved processutilizing a cytoplasmic-genetic male sterile system for the productionof F₁ hybrid cottonseeds wherein a marker system is utilized for puritycontrol which is readily identifiable, is highly reliable, and is notinfluenced by the environment.

It is another object of the present invention to provide an improvedprocess for forming F₁ hybrid cottonseeds wherein the requiredcross-pollination readily can be carried out with the aid ofpollen-carrying insects.

It is another object of the present invention to provide an improvedprocess for forming F₁ hybrid cottonseeds wherein an abundant andconsistent supply of pollen is provided by the male parent plants.

It is yet another object of the present invention to provide an improvedprocess for forming F₁ hybrid cottonseeds wherein pollen-carryinginsects are provided good accessibility to amply exposed flowers of themale parent plants.

It is a further object of the present invention to provide an improvedprocess for forming F₁ hybrid cottonseeds wherein the respective parentplants and the resulting F₁ hybrid plants can be readily identifiedvisually thereby facilitating a more positive identification of fieldplots.

These and other objects, as well as the scope, nature, and utilizationof the claimed process, will be apparent to those skilled in the artfrom the following detailed description and appended claims.

SUMMARY OF THE INVENTION

It has been found that an improved process for the efficient productionof seeds capable of growing F₁ hybrid cotton plants comprises:

(a) growing in a planting area a substantially random population of (i)broad-leafed male sterile cotton plants wherein the broad leafconfiguration is attributable to a recessive gene pair for suchcharacteristic and the male sterility is attributable to the combinationof an atypical Cms cytoplasm and a recessive genetic system for malesterility, and (ii) narrow-leafed male fertile cotton plants wherein thenarrow leaf configuration is attributable to a partially dominant genepair for such characteristic and the male fertility is attributable to adominant genetic system for fertility restoration;

(b) pollinating the substantially random population of cotton plantswhereby cottonseeds are formed on the male sterile cotton plants (i)which are capable of growing male fertile F₁ hybrid cotton plants whichpossess a visually observable heterozygous leaf configuration that isintermediate in configuration between the leaf configurations of parentplants (i) and (ii), and cottonseeds are formed on the narrow-leafedmale fertile cotton plants (ii) which are capable of growingnarrow-leafed non-hybrid cotton plants;

(c) recovering cottonseeds which have formed on the substantially randompopulation of cotton plants in the planting area;

(d) growing at least a portion of the cottonseeds recovered in step (c);and

(e) determining the approximate proportion of F₁ hybrid cottonseedspresent in the cottonseeds recovered in step (c) on the basis of therespective leaf shapes of the plants grown in step (d).

It further has been found that an improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plantscomprises:

(a) growing a substantially uniform first population of broad-leafedmale sterile cotton plants wherein the broad leaf configuration isattributable to a recessive gene pair for such characteristic and themale sterility is attributable to a combination of an atypical Cmscytoplasm and a recessive genetic system for male sterility inpollinating proximity to a substantially uniform second population ofnarrow-leafed male fertile cotton plants wherein the narrow leafconfiguration is attributable to a partially dominant gene pair for suchcharacteristic and the male fertility is attributable to a dominantgenetic system for fertility restoration;

(b) pollinating the broad-leafed male sterile cotton plants of the firstpopulation with pollen from the narrow-leafed male fertile cotton plantsof the second population whereby cottonseeds are formed on thebroad-leafed male sterile cotton plants of the first population whichare capable of growing male fertile F₁ hybrid cotton plants whichpossess a visually observable heterozygous leaf configuration that isintermediate in configuration between the leaf configurations of thebulk of the plants of the first and second populations;

(c) recovering the cottonseeds which have formed on the plants of thefirst population;

(d) growing at least a portion of the cottonseeds recovered in step (c);and

(e) determining the approximate proportion of F₁ hybrid cottonseedspresent in the cottonseeds recovered in said step (c) on the basis ofthe respective leaf shapes of the plants grown in step (d).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a representative leaf configuration for a broad-leafedfemale fertile male sterile cotton plant which is suitable for use inthe improved process of the present invention.

FIG. 2 shows a representative leaf configuration for a narrow-leafed(i.e., okra-leafed) male fertile cotton plant which is suitable for usein the improved process of the present invention.

FIG. 3 shows a representative leaf configuration for an F₁ hybrid cottonplant which has resulted from the growing of the cottonseed formed inaccordance with the process of the present invention. It will be notedthat this leaf configuration is visually observable to be heterozygousand is intermediate in configuration between those of the parent plantsillustrated in FIGS. 1 and 2.

It should be understood that the specific number of lobes present on agiven cotton plant leaf may vary as described herein and is possiblyinfluenced by genetic factors, the location of the leaf on the cottonplant, and the environment.

DESCRIPTION OF PREFERRED EMBODIMENTS

The cytoplasmic-genetic system for hybrid cotton production utilized inthe process of the present invention is known and has previously beenreported in the literature by researchers such as Vesta G. Meyer andJames B. Weaver, Jr. The present invention provides for the first time areliable procedure for the efficient determination and maintenance ofthe desired level of purity in the hybrid cottonseed product.

In accordance with the concept of the present invention male sterilefemale, fertile cotton plants are selected for use as the seed parentswhich additionally have the usual broad leaf configuration. Such broadleaf configuration is attributable to a recessive gene pair for suchcharacteristic (e.g., gene pair 11). FIG. 1 illustrates a typical cottonleaf having such broad leaf configuration. As will be apparent to thoseskilled in cotton plant leaf morphology, not all leaves on a givencotton plant will likely possess five lobes as illustrated. Forinstance, cotton plant leaves having from 1 to 5 lobes commonly will beencountered with 3 to 5 lobes per leaf being the more frequent. Itfurther will be apparent to those skilled in cotton plant leafmorphology that the first leaves formed on a given cotton plant willtend to have a lesser number of lobes. Regardless of the number of lobespresent, the cotton plant leaf lobes of the female parent will besubstantially wider than those of the male parent discussed hereafterand readily distinguished in the adult plant. Also, the degree ofcleavage or division between adjoining leaf lobes of the female parentwill be substantially less.

Broad-leafed female parents are selected for use in the process of thepresent invention in which the male sterility is attributable to anatypical Cms (i.e., cytoplasmic male sterile) cytoplasm and a recessivegenetic system for male sterility. In such recessive genetic system theappropriate genes are present in combination with the Cms cytoplasm forthe male sterility characteristic to be expressed on a reliable basis.The male sterile cotton plants utilized by necessity possess at leastone pair of recessive genes (e.g., rfrf) which are incapable ofrestoring male fertility. Additionally, such male sterile female parentplants may possess either the dominant gene pair (e.g., EE) or therecessive gene pair (e.g., ee) for enhancing fertility restoration.However, if the narrow-leafed male parent plants (described hereafter)lack the dominant gene pair for enhancing fertility restoration EE, itis recommended that these genes be present in the broad-leafed malesterile plants. Good results have been achieved when the male sterilefemale parents possess the Cms cytoplasm in combination with therecessive rfrf and ee gene pairs. Since the required Cms cytoplasm isnot transmitted through the pollen, it can be considered cytoplasmic,non-Mendelian, extrachromosomal, uniparental, and maternal.

The male sterile cotton plants utilized in the process of the presentinvention are fully female fertile but produce no viable pollen, therebyprecluding the possibility of unwanted self-pollination. These plantsaccordingly can satisfactorily serve as the female or seed parents whileusing the hybridization procedures described hereafter. Accordingly, allseeds formed on the male sterile cotton plants following pollination bythe male parent will be capable of forming the desired F₁ hybrid cottonplants having a distinctive heterozygous leaf configuration (describedhereafter).

Cytoplasmically male sterile cotton plants having the requisite geneticmakeup in combination with the broad leaf configuration previously havebeen reported and presently are available from many public and privatecotton breeding programs. Such plants commonly possess a Gossypiumharknessii Brandg. cytoplasm in combination with the requisite genes forbroad leaf configuration and male sterility. Respresentative sources forseeds capable of forming the cytoplasmically male sterile cotton plantsare Texas A & M University (College Station, Texas), Mississippi StateUniversity (State College, Mississippi), New Mexico State University(University Park, New Mexico), University of Georgia (Athens, Georgia),etc. Good results have been obtained when using Tamcot A-788 as thecytoplasmically male sterile cotton plants. Such Tamcot A-788cytoplasmic male sterile line was developed in the Texas A & MUniversity system and has been available since 1979 from the TexasAgricultural Experiment Station, Route No. 3, Lubbock, Texas 79401.Also, seeds derived from Tamcot A-788 through selection have beendesignated No. RA-A30 and have been deposited in the National SeedStorage Laboratory at Fort Collins, Colo., under Laboratory AccessionNo. GH-2375 Ser. No. 190,936.

The requisite cytoplasmic and genetic makeup for the broad-leafed malesterile female parent can be readily transferred to other existingvarieties or lines (e.g., those of the Gossypium hirsutum L. genotype)by the backcross technique using the previously available male sterilecotton plants as the female parents and the variety or line of Gossypiumhirsutum as the recurring male parent for a number of generations (e.g.,four or five generations). The offspring will be female fertile andcytoplasmic male sterile, and the male sterile and maintainer lines willthen be substantially identical in their genetic complement.

Once the broad-leafed male sterile plants for use in the process of thepresent invention are selected, they may be maintained and multiplied bycrossing with suitable maintainer plants which lack the atypical Cmscytoplasm but otherwise include a recessive genetic system for malesterility (e.g., rfrf and ee gene pairs or rfrf and EE gene pairs) andthe recessive genes for a broad leaf configuration. Such maintainerplants will possess a cytoplasm of the normal type (i.e., an Ncytoplasm). It has been found that cotton plants of Gossypium hirsutumgenotype can be used to develop suitable maintainer lines.Representative sources for seeds capable of forming satisfactorymaintainer cotton plants for specific cytoplasmically male sterilecotton plants are Texas A & M University, Mississippi State University,New Mexico State University, University of Georgia, etc. A goodmaintainer for the cytoplasmically male sterile Tamcot A-788 cottonplants is the Tamcot 788 line. The Tamcot 788 line was developed in theTexas A & M University system and is available from the TexasAgricultural Experiment Station, Route No. 3, Lubbock, Tex. 79401. TheTamcot A-788 cytoplasmically male sterile line was developed from thisTamcot 788 line. Seeds derived from the Tamcot 788 line throughselection have been designated No. RA-B30 and have been deposited in theNational Seed Storage Laboratory at Fort Collins, Colo., underLaboratory Accession No. GH-2376 Ser. No. 190,937.

Also, commercially available varieties or lines of Gossypium hirsutummay be used as suitable maintainer lines provided they carry therequisite genes for a broad leaf configuration and possess asubstantially identical genetic complement to that of thecytoplasmically male sterile cotton plants. As will be apparent to thoseskilled in plant breeding, the specific cytoplasmically male sterile andmaintainer plants selected will be influenced by the growing area inwhich the F₁ hybrid plants are ultimately to be grown. For instance,under appropriate circumstances varieties such as Stoneville 825,Paymaster 404, Acala 1517-70, Deltapine 61, DES 024, Tamcot SP37H, etc.,may be used as maintainer plants provided one first has developed therequired cytoplasmically male sterile plants having a substantiallyidentical genetic complement by the backcross technique as previouslydescribed. Also, as will be apparent to those skilled in planttechnology, the choice will often be influenced by the combining abilitywith the fertility restoring male parent (discussed hereafter) which ischosen for the production of the F₁ hybrid in accordance with theprocess of the present invention.

In accordance with the concept of the present invention, male fertilecotton plants are selected for use as the male parents whichadditionally have the less frequently encountered narrow-leafedconfiguration. Such narrow leaf configuration is attributable to apartially dominant gene pair (e.g., LL) for such characteristic. Suchdominance by necessity is incomplete, in the sense that when crossedwith the female parents, an F₁ hybrid is produced having a heterozygousleaf configuration that is intermediate in configuration between theleaf configurations of the parent plants (as described hereafter). FIG.2 illustrates a typical cotton leaf having a narrow leaf configuration(i.e., an okra leaf configuration). As will be apparent to those skilledin cotton plant leaf morphology, not all leaves present on a givencotton plant are likely to possess the exact number of lobes illustratedin FIG. 2. Regardless of the number of lobes present, the leaf lobes ofthe male parent will be substantially narrower than those of the femaleparent previously discussed and readily distinguished in the adultplant. Also, there will be readily observable deeper cleavage ordivision between the adjoining cotton plant leaf lobes of the maleparent. In addition to the okra leaf configuration illustrated in FIG.2, other narrow-leafed configurations attributable to a dominant genepair, such as sub-okra, super-okra, laciniate, etc., may be selected.Such various narrow-leafed configurations may be attributable to thefollowing gene pairs as reported in the literature:

    ______________________________________                                                         Partially                                                    Narrow           Dominant                                                     Leaf Configuration                                                                             Gene Pairs                                                   ______________________________________                                        okra             L°L°                                           sub-okra         L.sup.u L.sup.u                                              super-okra       L.sup.s L.sup.s                                              laciniate        L.sup.1 L.sup.1.                                             ______________________________________                                    

The preferred leaf configuration for the narrow-leafed male fertilecotton plants is okra-leaf substantially as illustrated in FIG. 2.

The narrow-leafed male fertile cotton plants which are employed in theprocess of the present invention are fully male fertile (i.e., theyproduce an ample quantity of viable pollen to accomplish the desiredcross-pollination) and are capable through a dominant genetic system ofrestoring fertility in the F₁ hybrid when crossed with theaforementioned male sterile plants. For instance, such narrow-leafedmale fertile plants must possess a pair of dominant fertility restoringgenes (e.g., RfRf). Additionally, if the broad-leafed male sterilefemale parent lacks the dominant gene pair for enhancing fertilityrestoration (e.g., EE), then it is recommended that such genes beprovided in the male parent in the dominant form, and not in therecessive form (e.g., ee). The cytoplasm of the narrow-leafed malefertile cotton plants may be either cytoplasmic or normal, andpreferably is cytoplasmic since plants with weak fertility genes can bemore readily identified and removed. The flowers containing viablepollen preferably are produced in abundance as is a characteristic ofmany narrow-leafed cotton varieties. It also is preferable to select asmale parents those cotton plant varieties which flower as soon as orbefore the female parents. Accordingly, pollen is present when the firstblossoms appear on the male sterile female parents and the blossomingtimes are well synchronized. Such synchronization can be enhanced byplanting the two diverse parents at different times taking intoconsideration their respective ages when blossoming commonly occurs.

The narrow-leafed male fertile cotton plants which are employed in theprocess of the present invention may be obtained from existing cottongerm plasms by conventional selection and breeding techniques. Forinstance, Dr. James B. Weaver, Jr., of the University of Georgia(Athens, Ga.) has discussed in the technical literature and is makingavailable to plant researchers a number of cotton stocks which possessthe requisite dominant genetic system for fertility restoration whencrossed with cytoplasmically male sterile cotton plants. Such fertilityrestoring cotton stocks which are available from the University ofGeorgia have been identified by the Demeter I, Demeter II, and DemeterIII designations. Also, Mississippi State University through the DeltaAgricultural Experiment Station, Stoneville, Miss., is making availablea cotton stock which possesses the requisite genetic system forfertility restoration under the DES 146C designation. Alternatively, therequisite genetic system for fertility restoration may be obtained froma commercially available F₁ hybrid cotton which was produced using suchsystem such as the RA 3433H cotton hybrid. While using this source,subsequent generations of the cotton hybrid are grown out and selectionsare made for full fertility in the third and fourth generations toidentify plants which are homozygous dominant for fertility restoration(i.e., plants which possess RfRf and EE gene pairs).

Once the requisite dominant genetic system for fertility restoration isconfirmed, it may be added by crossing to standard narrow-leafed cottonstocks (e.g., the Pronto, Gumbo, etc., varieties). Also, a good sourcefor cotton stocks possessing a narrow-leafed configuration (e.g., anokra-leafed configuration) is Louisiana State University (Baton Rouge,La.).

Seeds capable of forming narrow-leafed male fertile cotton plants foruse in the process of the present invention when the broad-leafed malesterile plants are Tamcot A-788 or RA-A30 have been designated No.RA-R511-80-1 and have been deposited in the National Seed StorageLaboratory at Fort Collins, Colo., under Laboratory Accession No.GH-2374 Ser. No. 190,935. Such male parent stock was derived throughselection from Demeter II which was obtained from the University ofGeorgia. Numerous other narrow-leafed male fertile cotton plant linescould be similarly derived and selected for use in the process of thepresent invention.

When carrying out the improved process for the efficient production ofseeds capable of growing F₁ hybrid cotton plants in accordance with thepresent invention, the requisite parent plants heretofore described canbe grown as either (1) a substantially random cotton plant population,or (2) as substantially uniform cotton plant populations of each parentwhich are grown in pollinating proximity to each other. The seedsrequired to produce the parent plants can be planted and cultivated inaccordance with conventional cotton-growing procedures. For instance,the cotton seeds may be planted at a density of approximately 4 to 6seeds per foot in rows having a width of approximately 32 to 40 inches.It is preferable that the parent plants be grown at an area which isisolated from other cotton plants so as to minimize the occurrence ofoutcrossing pollination from an unwanted source.

In a preferred embodiment of the process of the present invention, thecottonseed lots capable of producing the two parents are blended to forma substantially uniform random mixture prior to planting. An adequatenumber of the narrow-leafed male fertile plants are planted to provideample pollen for the seed parent plants growing in the same area. Thenarrow-leafed male fertile plants commonly flower prolifically and henceare excellent pollen producers with good flower accessibility. Theyoften can be provided in substantially lesser numbers than the femaleparent plants. For instance, the parent cottonseeds frequently can beblended prior to planting so that the resulting substantially randompopulation of cotton plants comprises approximately 85 to 95 percent bya number of plants of the broad-leafed male sterile parent, andapproximately 5 to 15 percent by number of plants of the narrow-leafedmale fertile parent. In a particularly preferred embodiment of theprocess of the present invention, the substantially random population ofcotton plants comprises approximately 90 to 95 percent by number ofplants of the broad-leafed male sterile parent, and approximately 5 to10 percent by number of plants of the narrow-leafed male fertile parent.

Alternatively, in another embodiment of the process of the presentinvention wherein substantially uniform populations of each parent areprovided, the respective populations are grown sufficiently near to eachother so that pollen can be transferred without loss of viability. Forinstance, the two types of parent cotton plants can be grown adjacent toeach other as alternating strips. Such strips preferably take theconfiguration of adjoining rows which are planted with conventionalcotton planting equipment. For instance, the substantially uniformpopulation of broad-leafed male sterile cotton plants may consist ofapproximately 2 to 16 adjoining rows (e.g., 4 adjoining rows) whichalternate with approximately 2 to 4 adjoining rows (e.g., 2 adjoiningrows) of the narrow-leafed male fertile cotton plants.

Once the respective plants reach sufficient maturity to blossom, pollenis transferred from the narrow-leafed male fertile cotton plants to thebroad-leafed male sterile cotton plants by any appropriate technique.The broad-leafed male sterile plants undergo cross-pollination and thenarrow-leafed male fertile plants undergo self-pollination. In apreferred embodiment of the present process, the pollination is carriedout with the aid of pollen-carrying insects that reliably visit thecotton blossoms. In a particularly preferred embodiment of the process,the pollination is carried out with the aid of honeybees. It has beenfound that more efficient cross-pollination can be carried out by agiven quantity of bees if the respective parents are grown in rows inbulk as a substantially random population, since pollen-carrying insectssuch as honeybees have been found to demonstrate a greater propensity totravel along a given row of cotton plants than to travel from one row toanother. During the pollination process of the present invention, it isrecommended that the native bee population be augmented by hives ofdomesticated honeybees which are provided adjacent or within theplanting area where the F₁ hybrid cottonseeds are produced. Suchhoneybee hives may be provided in a concentration of approximately 1 to6 hives per acre. The beehives should, of course, be protected whenspraying of the cotton-growing area with an insecticide takes place.

At the appropriate time in the life cycle of the cotton plants, thecottonseed product is harvested using conventional technology and thecottonseeds are recovered taking care to avoid contamination withcottonseeds from a foreign source. In an embodiment of the process inwhich both parents are grown as a substantially random population, thecottonseed product can be simply harvested from the entire planting areawithout any attempt to harvest separately the F₁ hybrid cottonseedsformed on the male sterile parents. Alternatively, in the embodiment ofthe process in which each parent is grown separately as a substantiallyuniform population, the cottonseed products formed on each parent areseparately harvested taking care not to mix the same. In such instancethe cottonseeds formed on the female parent plants are capable offorming male fertile F₁ hybrid cotton plants and the cottonseeds formedon male parent plants will form non-hybrid cotton plants. Suchnon-hybrid product can be disposed of appropriately.

Next, at least a portion of the cottonseeds obtained from the area wherethe male sterile plants were grown are planted and the resulting plantsare observed with respect to leaf shape configuration. Morespecifically, a representative sample of such cottonseeds (e.g., aquantity preferably of at least one pound) is planted. When the cottonplants have developed to sufficient maturity to observe their leafconfigurations, the number of cotton plants having a heterozygous leafconfiguration which is intermediate to that of the leaf configurationsof the parents is determined (preferably by visual observation) and iscompared to the total number of plants from this cottonseed source. Atypical heterozygous leaf configuration for a F₁ hybrid cotton plantderived from a male sterile broad-leafed parent pollinated by a maleparent having an okra leaf configuration is illustrated in FIG. 3. Suchplant would possess the gene pair L° 1° with respect to leafconfiguration. As will be apparent to those skilled in cotton plant leafmorphology, not all leaves present on a given cotton plant are likely topossess the exact number of lobes illustrated in FIG. 3. Regardless ofthe number of lobes present, the desired F₁ hybrid cotton plants willpossess an observable intermediate leaf phenotype which may be readilydistinguished from each parent.

Accordingly, the improved procedure for forming F₁ hybrid cottonseeds ofthe present invention is readily amenable to the determination andmaintenance of a relatively high level of purity in the F₁ hybridcottonseed product. In accordance with the concept of the presentinvention, frequently at least 75 percent of the cottonseeds recoveredare capable of growing F₁ hybrid cotton plants on the basis of thedetermination previously described. Preferably, at least 90 percent ofthe cottonseeds recovered are capable of growing F₁ hybrid cottonplants, and most preferably, at least 95 percent of the cottonseedsrecovered are capable of growing F₁ hybrid cotton plants on the basis ofsuch determination. The determination of the relative purity of the F₁hybrid cottonseed product is greatly simplified when compared to thelaborious testing commonly required in the prior art. Thus, the seedproducer can reliably ascertain the F₁ hybrid content of the seed toguide him in the accurate labeling and marketing of the seed. Also, thegrower can be reliably informed in advance of the hybrid content of theplanting seed he has purchased and can plan his agronomic practicesaccordingly.

While it is always the desire of seedsmen to maintain 100 percent purityin the foundation seed, this as a practical matter proves to be anelusive goal. In accordance with a preferred embodiment of the improvedprocess of the present invention, the sources for the parental plantsand/or the parental plants themselves, when grown as substantiallyuniform populations, are carefully monitored for the requisite leafshape configurations. This may be done by visually observing the malesterile female parent line and its maintainer cotton plants and simplydestroying any plants which fail to exhibit the required broad-leafedconfiguration. Also, one may visually observe the male fertile parentline and destroy any cotton plants which fail to exhibit the requirednarrow-leafed configuration. Any heterozygous leaf configurations whichshow up in either parent are recognized as an undesired outcross. Suchan outcross may be destroyed by hand-roguing or by any other appropriatetechnique. The purity of the parent lines is accordingly enhanced as isthe purity of the ultimate F₁ hybrid product which is producedtherefrom. Without the process of the present invention it would havebeen necessary to detect unwanted male fertility or sterility by atedious test-cross procedure involving much record keeping and thelaborious tagging of large numbers of cotton plants. Accordingly, theprocess of the present invention overcomes significant disadvantageswhich have resided in the prior art and holds the promise of makinghybrid cotton a reality to the farmer at a reasonable cost.

Hybrid cotton plants made possible by the process of the presentinvention were evaluated during 1983 in tests which were carried out bythe Texas A & M University Agriculture Research and Extension Center atLubbock, Tex. Data from these tests is reported in a memo publicationentitled "Cotton Variety Tests in the Texas High Plains," 1983. Onehybrid variety made possible by the process of the present invention wasdesignated RAX-4507 and was found to yield 760 pounds of cotton lint peracre. Under the same growing conditions, a non-hybrid cotton varietyknown as Paymaster 404 which presently is widely grown on a commercialbasis yielded 693 pounds of cotton lint per acre. Accordingly, anincrease in yield of 67 pounds per acre was made possible with theresulting F₁ cotton hybrid during these tests.

Although the invention has been described with preferred embodiments, itis to be understood that variations and modifications may be resortedto, as will be apparent to those skilled in the art. Such variations andmodifications are to be considered within the purview and scope of theclaims appended hereto.

We claim:
 1. An improved process for the efficient production of seedscapable of growing F₁ hybrid cotton plants comprising:(a) growing in aplanting area a substantially random population of (i) broad-leafed malesterile cotton plants wherein the broad leaf configuration isattributable to a recessive gene pair for such characteristic and saidmale sterility is attributable to the combination of an atypical Cmscytoplasm and a recessive genetic system for male sterility, and (ii)narrow-leafed male fertile cotton plants wherein the narrow leafconfiguration is attributable to a partially dominant gene pair for suchcharacteristic and said male fertility is attributable to a dominantgenetic system for fertility restoration; (b) pollinating saidsubstantially random population of cotton plants whereby cottonseeds areformed on said male sterile cotton plants (i) which are capable ofgrowing male fertile F₁ hybrid cotton plants which possess a visuallyobservable heterozygous leaf configuration that is intermediate inconfiguration between the leaf configurations of parent plants (i) and(ii), and cottonseeds are formed on said narrow-leafed male fertilecotton plants (ii) which are capable of growing narrow-leafed non-hybridcotton plants; (c) recovering cottonseeds which have formed on saidsubstantially random population of cotton plants in said planting area;(d) growing at least a portion of the cottonseeds recovered in step (c);and (e) determining the approximate proportion of F₁ hybrid cottonseedspresent in said cottonseeds recovered in said step (c) on the basis ofthe respective leaf shapes of said plants grown in step (d).
 2. Animproved process for the efficient production of seeds capable ofgrowing F₁ hybrid cotton plants according to claim 1 wherein saidsubstantially random population of cotton plants (i) and (ii) which isgrown in step (a) is planted within rows.
 3. An improved process for theefficient production of seeds capable of growing F₁ hybrid cotton plantsaccording to claim 1 wherein said substantially random population ofcotton plants (i) and (ii) which is grown in said planting area in step(a) comprises approximately 85 to 95 percent of (i) plants andapproximately 5 to 15 percent of (ii) plants, based upon tne totalnumber of cotton plants growing in said planting area.
 4. An improvedprocess for the efficient production of seeds capable of growing F₁hybrid cotton plants according to claim 1 wherein said substantiallyrandom population of cotton plants (i) and (ii) which is grown in saidplanting area in step (a) comprises approximately 90 to 95 percent of(i) plants and approximately 5 to 10 percent of (ii) plants, based uponthe total number of cotton plants growing in said planting area.
 5. Animproved process for the efficient production of seeds capable ofgrowing F₁ hybrid cotton plants according to claim 1 wherein the broadleaf configuration of said male sterile cotton plants (i) isattributable to the recessive gene pair ll.
 6. An improved process forthe efficient production of seeds capable of growing F₁ hybrid cottonplants according to claim 1 wherein said narrow leaf configuration ofsaid male fertile cotton plants (ii) is attributable to the partiallydominant gene pair LL.
 7. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 1 wherein said narrow-leafed male fertile cotton plants (ii)possess a leaf configuration selected from the group consisting of okra,sub-okra, super-okra, laciniate, and mixtures of two or more of theforegoing.
 8. An improved process for the efficient production of seedscapable of growing F₁ hybrid cotton plants according to claim 1 whereinsaid narrow-leafed male fertile cotton plants (ii) possess an okra leafconfiguration which is attributable to the partially dominant gene pairL° L°.
 9. An improved process for the efficient production of seedscapable of growing F₁ hybrid cotton plants according to claim 1 whereinsaid pollination in step (b) is carried out with the aid ofpollen-carrying insects.
 10. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 1 wherein said pollination in step (b) is carried out with theaid of honeybees.
 11. An improved process for the efficient productionof seeds capable of growing F₁ hybrid cotton plants according to claim 1wherein at least 75 percent of the cottonseeds recovered in step (c) arecapable of growing F₁ hybrid cotton plants on the basis of thedetermination of step (e).
 12. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 1 wherein at least 90 percent of the cottonseeds recovered instep (c) are capable of growing F₁ hybrid cotton plants on the basis ofthe determination of step (e).
 13. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 1 wherein at least 95 percent of the cottonseeds recovered instep (c) are capable of growing F₁ hybrid cotton plants on the basis ofthe determination of step (e).
 14. An improved process for the efficientproduction of seeds capable of growlng F₁ hybrid cotton plants accordingto claim 1 wherein the parental plants for cotton plants (i) and (ii),as well as the maintainer plants for plants (i), were grown assubstantially uniform plant populations, the respective leafconfigurations in each such population were visually observed, andplants growing in such substantially uniform plant populations having anon-conforming leaf configuration were substantially destroyed so as toenhance the purity of the parental lines.
 15. An improved process forthe efficient production of seeds capable of growing F₁ hybrid cottonplants comprising:(a) growing a substantially uniform first populationof broad-leafed male sterile cotton plants wherein the broad leafconfiguration is attributable to a recessive gene pair for suchcharacteristic and said male sterility is attributable to a combinationof an atypical Cms cytoplasm and a recessive genetic system for malesterility in pollinating proximity to a substantially uniform secondpopulation of narrow-leafed male fertile cotton plants wherein thenarrow leaf configuration is attributable to a partially dominant genepair for such characteristic and said male fertility is attributable toa dominant genetic system for fertility restoration; (b) pollinatingsaid broad-leafed male sterile cotton plants of said first populationwith pollen from said narrow-leafed male fertile cotton plants of saidsecond population whereby cottonseeds are formed on said broad-leafedmale sterile cotton plants of said first population which are capable ofgrowing male fertile F₁ hybrid cotton plants which possess a visuallyobservable heterozygous leaf configuration that is intermediate inconfiguration between the leaf configurations of the bulk of the plantsof said first and second populations; (c) recovering the cottonseedswhich have formed on said plants of said first population; (d) growingat least a portion of the cottonseeds recovered in step (c); and (e)determining the approximate proportion of F₁ hybrid cottonseeds presentin said cottonseeds recovered in said step (c) on the basis of therespective leaf shapes of the plants grown in step (d).
 16. An improvedprocess for the efficient production of seeds capable of growing F₁hybrid cotton plants according to claim 15 wherein the substantiallyuniform populations of cotton plants of the first and second populationsare grown within rows in step (a).
 17. An improved process for theefficient production of seeds capable of growing F₁ hybrid cotton plantsaccording to claim 15 wherein said first population of broad-leafedcotton plants consists of approximately 2 to 16 adjoining rows andalternates with approximately 2 to 4 adjoining rows of saidnarrow-leafed male fertile cotton plants of said second population instep (a).
 18. An improved process for the efficient production of seedscapable of growing F₁ hybrid cotton plants according to claim 15 whereinsaid first population of broad-leafed male sterile cotton plantsconsists of approximately 4 adjoining rows and alternates withapproximately 2 adjoining rows of said narrow-leafed male fertile cottonplants of said second population in step (a).
 19. An improved processfor the efficient production of seeds capable of growing F₁ hybridcotton plants according to claim 15 wherein the broad leaf configurationof said male sterile cotton plants of said first population isattributable to the recessive gene pair ll.
 20. An improved process forthe efficient production of seeds capable of growing F₁ hybrid cottonplants according to claim 15 wherein said narrow leaf configuration ofsaid male fertile cotton plants of said second population isattributable to the partially dominant gene pair LL.
 21. An improvedprocess for the efficient production of seeds capable of growing F₁hybrid cotton plants according to claim 15 wherein said narrow-leafedmale fertile cotton plants of said second population possess a leafconfiguration selected from the group consisting of okra, sub-okra,super-okra, laciniate, and mixtures of two or more of the foregoing. 22.An improved process for the efficient production of seeds capable ofgrowing F₁ hybrid cotton plants according to claim 15 wherein saidnarrow-leafed male fertile cotton plants of said second populationpossess an okra leaf configuration which is attributable to thepartially dominant gene pair L° L°.
 23. An improved process for theefficient production of seeds capable of growing F₁ hybrid cotton plantsaccording to claim 15 wherein said crossing of step (b) is carried outwith the aid of pollen-carrying insects.
 24. An improved process for theefficient production of seeds capable of growing F₁ hybrid cotton plantsaccording to claim 15 wherein said crossing in step (b) is carried outwith the aid of honeybees.
 25. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 15 wherein at least 75 percent of the cottonseeds recovered instep (c) are capable of growing F₁ hybrid cotton plants on the basis ofthe determination of step (e).
 26. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 15 wherein at least 90 percent of the cottonseeds recovered instep (c) are capable of growing F₁ hybrid cotton plants on the basis ofthe determination of step (e).
 27. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 15 wherein at least 95 percent of the cottonseeds recovered instep (c) are capable of growing F₁ hybrid cotton plants on the basis ofthe determination of step (e).
 28. An improved process for the efficientproduction of seeds capable of growing F₁ hybrid cotton plants accordingto claim 15 wherein the substantially uniform first and secondpopulations of cotton plants were visually observed prior to step (b),and plants present therein having a nonconforming leaf configurationwere substantially destroyed so as to enhance the purity of therespective plant populations prior to crossing in step (b).